[TUHS] PDP-8 (was: 2.11BSD cross compiler)

[Greg 'groggy' Lehey]

On Tuesday, 28 September 2010 at 22:59:22 -0400, John Cowan wrote:
> On Tue, Sep 28, 2010 at 10:38 PM, Larry McVoy <lm at bitmover.com> wrote:
>
>> Color me old school.  I like MIPS, I worked at SGI (got married to
>> an old school MIPS gal) but PDP-11 is so frigging intuitive.  How
>> can you not understand that instruction set?  If you can't, well,
>> sorry, not so much in my book.  It's like a stripped down C.
>
> Yeah.  I used it on and off, but my serious assembler programming
> was on the PDP-8.  Now *that* was seriously small, but you had to
> know the tricks, like how to find out the absolute address of the
> 128-word memory page following the one you are on when writing PIC
> code for OS/8 device drivers, or how to microprogram the operate
> instructions get interesting constants into the AC.

That was my first machine too (well, a PDP-12, which was really a
hybrid PDP-8/LINC-8, but I only used the PDP-8 instructions).  That
was a nice, compact instruction set.  It has the great advantage that
I can still remember just about every instruction today.  Remember the
autoincrement registers?  Even in those days they looked like a
kludge, but they helped a lot.

>> Come on - has anyone ever seen a better instruction set?  More
>> complicated, yeah, holy moly, yeah.  But cleaner?  We owe DEC
>> for that one.
>
> I remember how appalled I was when I saw the VAX instruction set.
> Luckily, it didn't matter: I never did assembler again.  Still,
> trying to make people think in octal at this late date seems
> unnecessary.

It's funny how long octal clung on.  It should have gone away with 8
bit bytes.  But somehow I still have a soft spot for octal, and
numbers like 7778 still look wrong.

>> Personally, I like anyone who can do any assembler.  One of my interview
>> questions is "have you written swtch?"
>>
>>  If you don't get the question you are not an OS person,
>> if you are, of course you get it.

Hmm.  Am I expected to understand this?  Seriously, I don't know how
many people really wrote anything like swtch ().

Greg
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